Landscape

Landscape imagery is important to this poem. The natural landscape is described by the speakers in order to give a sense of the power of their own song and struggle for freedom. Nature is beautiful, it's powerful, and it nourishes us. In the same way, the speakers suggest that their song (which represents a wider struggle for freedom) is also beautiful and powerful and nourishing—just as powerful and nourishing as nature. It's like the song equivalent of the Grand Canyon: awesome.

• Lines 4-5: In describing their song as rising "High as the list'ning skies," the speakers suggest just how uplifting their song is. The image of the skies gives us a sense of endless height. The last we checked, the sky was way, way up there. And the speakers' song is so powerful that it reaches those magnificent heights. 
• Line 6: In this line, the speakers give us a sense of the power of their song through imagery associated with the sea. The speakers' song is so powerful that it's as loud as the "rolling sea." 
• Line 9: The image of the "rising sun" in this line is a metaphor for hope. The speakers suggest that the struggle for freedom will lead to a "new day" of brightness. The sun is bright and beautiful, and the future that the speakers look forward to is as bright and beautiful as the sun. 
• Line 21: The "white gleam" of the "bright star" described in this line again gives us a sense of the boundless hope that the speakers of this poem feel. The future is gleaming like a bright star. In this way, the beauty and the brightness of the star gives us a sense of the beauty and the brightness of the future that the speakers look forward to.